Development of a novel technique for geothermal energy extraction from backfilled mine stopes

Abstract

Underground mines are valuable sources of geothermal energy. The present study aims to understand the heat transfer phenomenon that takes place during heat extraction from backfilled stopes of underground mines. The proposed technique, currently patented by researchers at McGill University, is based on the novel idea of installing geothermal heat exchange tubes in backfilled mine stopes prior to backfill placement in the stope. To investigate the feasibility of the novel technique of heat extraction from backfilled mine stopes, numerical and experimental heat transfer studies are conducted. To assess the performance of a stope−coupled geothermal heat exchanger system, a numerical model is developed. The model is capable of considering the effect of heat conduction as well as natural convection. The results of the developed model are compared with those from existing ground-coupled heat exchanger models. To further validate the developed numerical model, a series of experimental tests are conducted using a small scale laboratory test setup built for this purpose. By introducing information gathered from a number of Canadian mines into the developed heat transfer model, effects of hydraulic conductivity, thermal conductivity, rate of heat extraction and arrangement of heat exchanger tubes are investigated. This study shows that by extracting geothermal energy from backfilled mine stopes, an underground mine can be converted into a sustainable source of geothermal heat, rather than an enduring economic liability. By using this techniques heat mining can take place along with ore extraction from a mine and can continue after the depletion of the ore. Exploiting the geothermal sources of underground mines can supply mining communities with inexpensive and clean geothermal energy, and increase the sustainability of the mining industry.